Morphology of the cisterna chyli in nine dogs with idiopathic chylothorax and in six healthy dogs assessed by computed tomographic lymphangiography.

Objective: To describe the morphology of the lymphatics in the region of the cisterna chyli in healthy dogs and in dogs with idiopathic chylothorax by using computed tomographic lymphangiography.

Study design: Retrospective study.

Animals: Nine dogs with idiopathic chylothorax and six healthy dogs.

Methods: Computed tomographic lymphangiograms were reviewed to evaluate the number of cisterna chyli branches, total cross-sectional area of the branches normalized to the cross-sectional area of the aorta, number of branches with cross-sectional area greater than 25% of the aorta cross-sectional area, and ratio of the total perimeter to the total cross-sectional area of the branches. Data (mean ± SD) were compared between unaffected dogs and dogs with idiopathic chylothorax.

Results: The cisterna chyli included more branches in dogs with chylothorax (4.30 ± 1.57) than in unaffected dogs (1.67 ± 0.56, P = .02), occupying a relative perimeter approximately double that in unaffected dogs (P < .001). The relative cross-sectional area of the cisterna chyli was approximately twofold smaller in affected (0.73 ± 0.35) than in unaffected (1.63 ± 0.91, P = .02) dogs. The fraction of dogs with branches greater than 25% of the cross-sectional area of the aorta tended to be larger in unaffected dogs (P = .07). Most larger branches were located dorsal or to the right of the aorta.

Conclusion: The cisterna chyli of dogs with idiopathic chylothorax contained smaller and more numerous branches compared with that of unaffected dogs.

Clinical significance: Altered cisterna chyli morphology may impact the surgical approach for cisterna chyli ablation in dogs with idiopathic chylothorax.